High temperature thermoset compositions are useful in many demanding applications including molding resins, composite matrix resins, adhesives, coatings, blends, etc. Significant effort has been expended over the past several decades in the development of such materials whereby several viable resin systems have been identified and adapted for various applications with varying degrees of success. Of initial importance is the facile processability of the resin material prior to curing. Ideally, the material should be readily workable in such state so as to facilitate its molding, compositing or adherence to a surface, etc., as may be required for a particular application. Additionally, the material should remain stable in such state for an extended period of time. Of course, of ultimate importance are the material's properties after curing wherein a high glass transition temperature and the ability to retain certain properties at elevated temperatures for extended periods of time are particularly desirable. Another very important consideration is the cost of production of the resin including both the costs of the starting materials as well as the amount and complexity of the processing that is required.
Several strategies have to date been employed in an effort to achieve such goals. One fairly successful strategy has been to attach thermally activated (cross-linkable) groups to the side or end of thermally stable aromatic polymers (oligomers) such as polysulfones and/or polyimides. Several reactive group candidates have been considered including cyanate, benzocyclobutene, maleimide, ethynyl, phenylethynyl, phenylmaleimide, nadimide, norbornene, etc. The reactive groups can be incorporated either during the polymerization step or attached in a separate step to a preformed polymer. The reactive group will have to withstand the synthetic conditions (e.g., aromatic nucleophilic displacement reactions used to prepare poly(arylene ether)s and cure to give a structure with long term high temperature stability. For example, the high performance PMR family of thermoset resins comprises dialkylester of an aromatic tetracarboxylic acid, an aromatic diamine and a monoalkyl ester of 5-norbornese-2,3-dicarboxylic acid. Another useful high temperature thermoset resin is the LaRC-PETI phenylethynyl terminated imide system developed at NASA Langley research center. The curing of the phenylethynyl end groups results in chain extension and possible cross-linking of the imide structure.
While the continued development of heretofore known resin systems has yielded increases in glass transition temperatures and enhanced stability, such progress has typically amounted to mere incremental enhancements and often requires the use of expensive starting materials and/or complex processing. It is therefore most desirable to provide a new family of high temperature thermosetting resins with which significant increases with regard to glass transition temperature and/or high temperature stability can be realized and which can be manufactured using inexpensive starting materials and simple procedures. Providing a new family of compositions with such advantages would serve to greatly expand the applications for thermosetting resin materials.